Immunohistochemical identification of syncytiotrophoblastic cells and megakaryocytes in pulmonary vessels in a fatal case of amniotic fluid embolism.

The histological diagnosis of amniotic fluid embolism (AFE) is based on finding amniotic fluid components in the pulmonary microvasculature. In addition to the distinctive constituents of AFE, placental and decidual tissue fragments as well as isolated trophoblastic cells and megakaryocytes are potentially detectable within pulmonary vessels. The identification of single syncytiotrophoblastic cells (STC), and their differentiation from circulating megakaryocytes (MK) within the lumen of small and medium-sized pulmonary vessels is difficult by classical morphological methods. In a fatal case of AFE, we have successfully detected the simultaneous presence of STC and MK in the pulmonary microvasculature by means of a panel of specific monoclonal (CD61-GpIIIa, beta-hCG) and polyclonal (FVIII-vW, hPL) antibodies. The immunohistochemical analysis for identification of STC and MK should provide more precise data on their incidence and distribution in physiological and pathological conditions as well providing new insights into their physiopathological implications and their correlation with AFE and other gynaecological complications.